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Caesar cipher

Caesar cipher, is one of the simplest and most widely known encryption techniques. The transformation can be represented by aligning two alphabets, the cipher alphabet is the plain alphabet rotated left or right by some number of positions.

When encrypting, a person looks up each letter of the message in the 'plain' line and writes down the corresponding letter in the 'cipher' line. Deciphering is done in reverse.
The encryption can also be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A = 0, B = 1,..., Z = 25. Encryption of a letter x by a shift n can be described mathematically as

Plaintext: tuoppi
cipher variations:
uvpqqj vwqrrk wxrssl xysttm yztuun
zauvvo abvwwp bcwxxq cdxyyr deyzzs
efzaat fgabbu ghbccv hicddw ijdeex
jkeffy klfggz lmghha mnhiib noijjc
opjkkd pqklle qrlmmf rsmnng stnooh

Decryption is performed similarly,

(There are different definitions for the modulo operation. In the above, the result is in the range 0...25. I.e., if x+n or x-n are not in the range 0...25, we have to subtract or add 26.)
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Atbash Cipher

Atbash is an ancient encryption system created in the Middle East. It was originally used in the Hebrew language.
The Atbash cipher is a simple substitution cipher that relies on transposing all the letters in the alphabet such that the resulting alphabet is backwards.
The first letter is replaced with the last letter, the second with the second-last, and so on.
An example plaintext to ciphertext using Atbash:
Plain: tuoppi
Cipher: gflkkr

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Baconian Cipher

To encode a message, each letter of the plaintext is replaced by a group of five of the letters 'A' or 'B'. This replacement is done according to the alphabet of the Baconian cipher, shown below.
a   AAAAA   g    AABBA     m    ABABB   s    BAAAB     y    BABBA
b   AAAAB   h    AABBB     n    ABBAA   t    BAABA     z    BABBB
c   AAABA   i    ABAAA     o    ABBAB   u    BAABB 
d   AAABB   j    BBBAA     p    ABBBA   v    BBBAB
e   AABAA   k    ABAAB     q    ABBBB   w    BABAA
f   AABAB   l    ABABA     r    BAAAA   x    BABAB

Plain: tuoppi

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Affine Cipher
In the affine cipher the letters of an alphabet of size m are first mapped to the integers in the range 0..m - 1. It then uses modular arithmetic to transform the integer that each plaintext letter corresponds to into another integer that correspond to a ciphertext letter. The encryption function for a single letter is

where modulus m is the size of the alphabet and a and b are the key of the cipher. The value a must be chosen such that a and m are coprime.
Considering the specific case of encrypting messages in English (i.e. m = 26), there are a total of 286 non-trivial affine ciphers, not counting the 26 trivial Caesar ciphers. This number comes from the fact there are 12 numbers that are coprime with 26 that are less than 26 (these are the possible values of a). Each value of a can have 26 different addition shifts (the b value) ; therefore, there are 12*26 or 312 possible keys.
Plaintext: tuoppi
cipher variations:

The decryption function is

where a - 1 is the modular multiplicative inverse of a modulo m. I.e., it satisfies the equation

The multiplicative inverse of a only exists if a and m are coprime. Hence without the restriction on a decryption might not be possible. It can be shown as follows that decryption function is the inverse of the encryption function,

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ROT13 Cipher
Applying ROT13 to a piece of text merely requires examining its alphabetic characters and replacing each one by the letter 13 places further along in the alphabet, wrapping back to the beginning if necessary. A becomes N, B becomes O, and so on up to M, which becomes Z, then the sequence continues at the beginning of the alphabet: N becomes A, O becomes B, and so on to Z, which becomes M. Only those letters which occur in the English alphabet are affected; numbers, symbols, whitespace, and all other characters are left unchanged. Because there are 26 letters in the English alphabet and 26 = 2 * 13, the ROT13 function is its own inverse:

ROT13(ROT13(x)) = x for any basic Latin-alphabet text x

An example plaintext to ciphertext using ROT13:

Plain: tuoppi
Cipher: ghbccv

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Polybius Square

A Polybius Square is a table that allows someone to translate letters into numbers. To give a small level of encryption, this table can be randomized and shared with the recipient. In order to fit the 26 letters of the alphabet into the 25 spots created by the table, the letters i and j are usually combined.
1 2 3 4 5
1 A B C D E
2 F G H I/J K
3 L M N O P
4 Q R S T U
5 V W X Y Z

Basic Form:
Plain: tuoppi
Cipher: 445443535342

Extended Methods:
Method #1

Plaintext: tuoppi
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
t u o p p i 
4 5 4 5 5 4 
4 4 3 3 3 2 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: tuoppi
Cipher: yyutnh

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Method #3

Plaintext: tuoppi
method variations:
ytxxsr txxsry xxsryt
xsrytx srytxx rytxxs

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Permutation Cipher
In classical cryptography, a permutation cipher is a transposition cipher in which the key is a permutation. To apply a cipher, a random permutation of size E is generated (the larger the value of E the more secure the cipher). The plaintext is then broken into segments of size E and the letters within that segment are permuted according to this key.
In theory, any transposition cipher can be viewed as a permutation cipher where E is equal to the length of the plaintext; this is too cumbersome a generalisation to use in actual practice, however.
The idea behind a permutation cipher is to keep the plaintext characters unchanged, butalter their positions by rearrangement using a permutation
This cipher is defined as:
Let m be a positive integer, and K consist of all permutations of {1,...,m}
For a key (permutation) , define:
The encryption function
The decryption function
A small example, assuming m = 6, and the key is the permutation :

The first row is the value of i, and the second row is the corresponding value of (i)
The inverse permutation, is constructed by interchanging the two rows, andrearranging the columns so that the first row is in increasing order, Therefore, is:

Total variation formula:

e = 2,718281828 , n - plaintext length

Plaintext: tuoppi

all 720 cipher variations:
tuoppi tuopip tuoppi tuopip tuoipp tuoipp tupopi tupoip tuppoi tuppio tupipo
tupiop tuppoi tuppio tupopi tupoip tupiop tupipo tuippo tuipop tuippo tuipop
tuiopp tuiopp touppi toupip touppi toupip touipp touipp topupi topuip toppui
toppiu topipu topiup toppui toppiu topupi topuip topiup topipu toippu toipup
toippu toipup toiupp toiupp tpoupi tpouip tpopui tpopiu tpoipu tpoiup tpuopi
tpuoip tpupoi tpupio tpuipo tpuiop tppuoi tppuio tppoui tppoiu tppiou tppiuo
tpiupo tpiuop tpipuo tpipou tpiopu tpioup tpopui tpopiu tpoupi tpouip tpoiup
tpoipu tppoui tppoiu tppuoi tppuio tppiuo tppiou tpupoi tpupio tpuopi tpuoip
tpuiop tpuipo tpipuo tpipou tpiupo tpiuop tpioup tpiopu tioppu tiopup tioppu
tiopup tioupp tioupp tipopu tipoup tippou tippuo tipupo tipuop tippou tippuo
tipopu tipoup tipuop tipupo tiuppo tiupop tiuppo tiupop tiuopp tiuopp utoppi
utopip utoppi utopip utoipp utoipp utpopi utpoip utppoi utppio utpipo utpiop
utppoi utppio utpopi utpoip utpiop utpipo utippo utipop utippo utipop utiopp
utiopp uotppi uotpip uotppi uotpip uotipp uotipp uoptpi uoptip uoppti uoppit
uopipt uopitp uoppti uoppit uoptpi uoptip uopitp uopipt uoippt uoiptp uoippt
uoiptp uoitpp uoitpp upotpi upotip upopti upopit upoipt upoitp uptopi uptoip
uptpoi uptpio uptipo uptiop upptoi upptio uppoti uppoit uppiot uppito upitpo
upitop upipto upipot upiopt upiotp upopti upopit upotpi upotip upoitp upoipt
uppoti uppoit upptoi upptio uppito uppiot uptpoi uptpio uptopi uptoip uptiop
uptipo upipto upipot upitpo upitop upiotp upiopt uioppt uioptp uioppt uioptp
uiotpp uiotpp uipopt uipotp uippot uippto uiptpo uiptop uippot uippto uipopt
uipotp uiptop uiptpo uitppo uitpop uitppo uitpop uitopp uitopp outppi outpip
outppi outpip outipp outipp ouptpi ouptip ouppti ouppit oupipt oupitp ouppti
ouppit ouptpi ouptip oupitp oupipt ouippt ouiptp ouippt ouiptp ouitpp ouitpp
otuppi otupip otuppi otupip otuipp otuipp otpupi otpuip otppui otppiu otpipu
otpiup otppui otppiu otpupi otpuip otpiup otpipu otippu otipup otippu otipup
otiupp otiupp optupi optuip optpui optpiu optipu optiup oputpi oputip opupti
opupit opuipt opuitp opputi oppuit opptui opptiu oppitu oppiut opiupt opiutp
opiput opiptu opitpu opitup optpui optpiu optupi optuip optiup optipu opptui
opptiu opputi oppuit oppiut oppitu opupti opupit oputpi oputip opuitp opuipt
opiput opiptu opiupt opiutp opitup opitpu oitppu oitpup oitppu oitpup oitupp
oitupp oiptpu oiptup oipptu oipput oipupt oiputp oipptu oipput oiptpu oiptup
oiputp oipupt oiuppt oiuptp oiuppt oiuptp oiutpp oiutpp puotpi puotip puopti
puopit puoipt puoitp putopi putoip putpoi putpio putipo putiop puptoi puptio
pupoti pupoit pupiot pupito puitpo puitop puipto puipot puiopt puiotp poutpi
poutip poupti poupit pouipt pouitp potupi potuip potpui potpiu potipu potiup
poptui poptiu poputi popuit popiut popitu poitpu poitup poiptu poiput poiupt
poiutp ptoupi ptouip ptopui ptopiu ptoipu ptoiup ptuopi ptuoip ptupoi ptupio
ptuipo ptuiop ptpuoi ptpuio ptpoui ptpoiu ptpiou ptpiuo ptiupo ptiuop ptipuo
ptipou ptiopu ptioup ppotui ppotiu ppouti ppouit ppoiut ppoitu pptoui pptoiu
pptuoi pptuio pptiuo pptiou pputoi pputio ppuoti ppuoit ppuiot ppuito ppituo
ppitou ppiuto ppiuot ppiout ppiotu piotpu piotup pioptu pioput pioupt pioutp
pitopu pitoup pitpou pitpuo pitupo pituop piptou piptuo pipotu pipout pipuot
piputo piutpo piutop piupto piupot piuopt piuotp puopti puopit puotpi puotip
puoitp puoipt pupoti pupoit puptoi puptio pupito pupiot putpoi putpio putopi
putoip putiop putipo puipto puipot puitpo puitop puiotp puiopt poupti poupit
poutpi poutip pouitp pouipt poputi popuit poptui poptiu popitu popiut potpui
potpiu potupi potuip potiup potipu poiptu poiput poitpu poitup poiutp poiupt
ppouti ppouit ppotui ppotiu ppoitu ppoiut ppuoti ppuoit pputoi pputio ppuito
ppuiot pptuoi pptuio pptoui pptoiu pptiou pptiuo ppiuto ppiuot ppituo ppitou
ppiotu ppiout ptopui ptopiu ptoupi ptouip ptoiup ptoipu ptpoui ptpoiu ptpuoi
ptpuio ptpiuo ptpiou ptupoi ptupio ptuopi ptuoip ptuiop ptuipo ptipuo ptipou
ptiupo ptiuop ptioup ptiopu pioptu pioput piotpu piotup pioutp pioupt pipotu
pipout piptou piptuo piputo pipuot pitpou pitpuo pitopu pitoup pituop pitupo
piupto piupot piutpo piutop piuotp piuopt iuoppt iuoptp iuoppt iuoptp iuotpp
iuotpp iupopt iupotp iuppot iuppto iuptpo iuptop iuppot iuppto iupopt iupotp
iuptop iuptpo iutppo iutpop iutppo iutpop iutopp iutopp iouppt iouptp iouppt
iouptp ioutpp ioutpp iopupt ioputp iopput iopptu ioptpu ioptup iopput iopptu
iopupt ioputp ioptup ioptpu iotppu iotpup iotppu iotpup iotupp iotupp ipoupt
ipoutp ipoput ipoptu ipotpu ipotup ipuopt ipuotp ipupot ipupto iputpo iputop
ippuot ipputo ippout ippotu ipptou ipptuo iptupo iptuop iptpuo iptpou iptopu
iptoup ipoput ipoptu ipoupt ipoutp ipotup ipotpu ippout ippotu ippuot ipputo
ipptuo ipptou ipupot ipupto ipuopt ipuotp iputop iputpo iptpuo iptpou iptupo
iptuop iptoup iptopu itoppu itopup itoppu itopup itoupp itoupp itpopu itpoup
itppou itppuo itpupo itpuop itppou itppuo itpopu itpoup itpuop itpupo ituppo
itupop ituppo itupop ituopp ituopp

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History of cryptography
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